Web特集
May 1, 2008
Series: Focus on Paint Market in Japan
Increasing demand for maintenance Life prolongation and Life Cycle Cost (LCC) reduction by anti corrosion coating
MLIT (Ministry of Land, Infrastructure, Transport and Tourism) estimate the number of the bridges over 50 years old will reach at 28,700 ten years, 68,200 twenty years later. That number means half of current (ca. 150,000) bridges over 15m-length.
Bridge for govern roads is being inspected every 5 years and damaged bridge is repaired every year. Bridge needing repair is found after regular inspection. The number of such repair needed bridge has been increasing year by year and it is too difficult to repair all.
Therefore, MLIT made mid term road plan (draft) last year and set out basic direction in 10- year plan for road construction since 2008. In the plan, it is clearly declared as goal to prolong lifetime of road bridge more than 100 years. In order to make life of bridge longer, MLIT try to detect spot for repair quickly through routine inspection and make proper action before reconstruction, huge repair is needed. MLIT requests local government to make same repair plan to prolong life of road.
Anti corrosion coating play important role of such a maintenance work. In terms of LCC reduction, Polyurethan resin and fluorine resin paint as topcoat is used to replace conventional phthalic acid basis or chlorinated rubber paint and obtain durability. In the market, solvent-born for new construction and fluorine resin paint based on weak-solvent for repair use became poplar after "Handbook of coating and heavy duty for road bridge" was revised 3 years ago. Recently, not only public office but also road constructor often qualifies formulation according to "specification in handbook".
The fluorine resin paint can reduce the number of repair work, which is usually repeated every 7 or 8 years, and prolong the bridge life with reducing LCC. Actually we can see construction data coated by fluorine resin paint 20 years ago. Paint producer can appeal its advantage based on actual performance data.
From now on, national budget for the maintenance of road bridge is expected to increase, paint manufacturer intends to enhance sales promotion with boarder product line to follow increasing demand for maintenance.
Demand trend on private sector
On the other hand, demand for maintenance is increasing in private sector. Since the economic bubble popped the maintenance work has not been budgeted, but it starts to run with business recovery. Current paint formulation is mainly required as LCC reduction type, not traditional industrial basis. In order to meet the requirement, paint producer prefers to propose polyurethane resin basis or fluorine resin paint with super weatherability. After "Handbook of coating" was revised, fluorine resin paint is often approved.
In addition, weak solvent type paint is penetrating the market because of operational advantage with no shrink and swell on the surface caused by no dissolution on under layer. Environment conscious customer is getting major and supports it as well.
Customer shows much interest in thicker coating due to cost reduction. It can perform by 2-layer coating such primer & base or base & top. As a result, we can make a film through 2 or 3 times operation instead of 4 times. This cut-down of process finally makes total cost reduction. Therefore, paint producer and job coater positively promote these coatings as differentiated product and can easily recommend to end-users. Practically, time saving formulation is mainly used for tower coating, as its term of works is very limited.
Main concern on thick coating is the execution management. Repair operation mostly runs by brush. If standard amount is not applied, the efficient film thickness is not coated, in a case under coat happen to be seen. In this case, recoat should be needed, it results in more time and task.
Best coating from environmentally friendly viewpoint is water-born paint. Now, some railway companies approve water born coating. JR (Japan Railway) East is coating around 10 bridges by water basis paint every year. Tokyo Metro starts to apply water basis coating to trial lines. Both companies follow "Guideline for coating execution on steel construction" issued by Railway Technical Research Institute. In the guideline, as ECO paint formulation, water born Epoxy resin paint for base coat and water top paint (resin type is not restricted) is qualified. However, as primer for spot repair, solvent born modified Epoxy resin basis thick paint is particularly approved.
It is difficult to manage execution control of water born paint, therefore, few paint supplier sell this paint freely. It has operational problem caused by change of climate and drying time, mostly paint supplier works together with customer for the running on site. Further improvement is required to make this paint commodity one.